Spirochetes of the genus Borrelia are the cause of relapsing fever, a remittant febrile disease, and are transmitted to man by lice or ticks. There is a paucity of knowledge of diagnostic serology, immunology, cultivation and genetics of Borrelia due to limited research in these areas. We propose to: develop a test for the serodiagnosis of borreleosis using purified surface components of Borrelia; examine the role of antibiotics and phagocytes in the elimination of borreliae from the host, evaluate the functions of different lymphocytes in the immune response to borreliae and study the nutritional and environmental requirement for the cultivation of Borrelia with the long term goal of developing a protein-free chemically defined culture medium. Finally, we propose to isolate the DAN from the presently recognized "species" of Borrelia and determine % Mol. G + C and genetic relatedness using DNA-DNA hybridization.